Plasma processing method

ABSTRACT

Provided is a plasma processing method capable of improving an etching selectivity of a material to be etched with respect to a mask material and reducing a roughness of a side wall of a mask pattern. The plasma processing method of selectively depositing a deposition film on the mask material with respect to the material to be etched includes controlling an etching parameter so that an incubation time of the mask material is shorter than an incubation time of the material to be etched.

TECHNICAL FIELD

The present invention relates to a plasma processing method.

BACKGROUND ART

In a manufacturing process of a semiconductor device and a manufacturingprocess of devices such as micro electro mechanical systems (MEMS), itis required to cope with miniaturization and integration of componentsincluded in the semiconductor device and the like. For example, in anintegrated circuit or a MEMS system, nanoscaling of a structure isfurther promoted.

In general, in the manufacturing process of the semiconductor devices, alithography technique is used to form a fine pattern. In this technique,a photoresist material is coated to a laminated thin film formed on asemiconductor substrate and is irradiated with ultraviolet rays or thelike by an exposure apparatus to transfer a circuit pattern of a photomask to the photoresist material, and a development processing isfurther performed to form a fine pattern of a photoresist. Thereafter,an etching processing using plasma is performed using a photoresistpattern as an etching mask, whereby a thin film can be selectivelyremoved and a pattern similar to the photo mask can be implemented as athree-dimensional object.

In recent years, in order to correspond to the acceleration of theminiaturization of large scale integration (LSI), the resolution of theexposure apparatus has been improved in a pattern transfer processperformed by the exposure apparatus. In general, in order to advance theminiaturization, it is necessary to improve a process constant (k1)determined by an exposure wavelength (λ), the number of lens apertures(NA), resist performance, and the transfer process. Recently, areduction in wavelength of the exposure wavelength by adopting an ArFlaser (wavelength: 193 nm) and an improvement of NA by using animmersion exposure technique have been carried out.

Further, a double patterning technique that divides the mask of thecircuit pattern into two masks, enlarges a minimum pitch of the exposurepattern, and improves k1 is also adopted. As for the double patterningtechnique, various methods relating to exposure and development havebeen proposed. For example, there are a double exposure method in whichexposure is continuously performed twice, a method of performing theetching processing after first exposure and then performing secondexposure, and a self-aligned method in which a spacer is formed afterpattern formation and the spacer is used as the mask pattern.

However, when a technique of performing exposure a plurality of times asdescribed above is used, problems such as an increase in processnumbers, a decrease in throughput, and an increase in manufacturing costoccur. Here, a patterning method based on an extreme ultraviolet (EUV)lithography technique using an extreme ultraviolet ray having awavelength of 13.5 nm and/or a directed self assembly (DSA) lithographytechnique using a self-assembly material has begun to be adopted.

The EUV lithography technique can achieve a resolution of 20 nm halfpitch or less by one exposure by using an extreme ultraviolet ray havinga wavelength of 13.5 nm, and is therefore adopted as an exposuretechnique responsible for the next generation of the ArF immersionlithography. In the EUV lithography technique, an extremely shortwavelength is used, and thus there is a maximum advantage that a highresolution can be obtained even with a low NA according to Rayleigh.

Theoretically, a resolution with a line width of 22 nm to 32 nm in thecase of NA=0.25, a resolution with a line width of 16 nm in the case ofNA=0.35, and a resolution with a line width of 10 nm or less in the caseof NA=0.4 or more can be obtained, and thus the EUV lithographytechnique is highly expected as an ultrafine pattern exposure technique.As a resist used in the EUV lithography technique (hereinafter referredto as an “EUV resist”), for example, a structure in which patterning isperformed on a silicon anti-reflection coating (SiARC), which is ananti-reflection film of a Si-containing material, or spin on glass (SOG)based on hydroxy silsesquioxane is generally adopted.

On the other hand, in the DSA lithography technique, a pattern is formedby utilizing phase separation of a material without requiring a specialexposure apparatus. As the self-assembly material, a diblock polymercontaining a hydrophilic polymer or a hydrophobic polymer is typicallyused, and typical examples thereof include a diblock polymer containingpolystyrene (hereinafter abbreviated as “PS”) and polymethacrylic acid(hereinafter abbreviated as “PMMA”). A patterning formation process ofthe DSA lithography technique is extremely simple, including onlycreating a guide pattern before coating the diblock polymer, forming aneutral film (hereinafter abbreviated as “NUL”), and baking after thecoating.

The pattern formation using the DSA lithography technique is also calleda dry development process because PMMA is dry-etched with plasma anddevelopment is performed after the pattern formation, and then, the NUL,which is a material to be etched, is etched using PS formed by the PMMAetching as a mask material.

In this way, examples of a feature of the mask pattern-formed by the EUVlithography technique and the DSA lithography technique includes thatthe mask is a thin film having a very low mask height. In the case ofthe EUV lithography technique, the mask height is generally 30 nm orless in view of the resolution of the resist, pattern collapse duringdevelopment, and the like. Meanwhile, in the case of the DSA lithographytechnique, the mask height is also generally 30 nm or less, which is thesame as a pitch width (PS width+PMMA width).

In this way, in the case of a thin film having a very low mask height,it is very important to selectively etch the film to be etched withrespect to the mask material. In addition, reduction in roughness of apattern edge is important along with the miniaturization, and inparticular, reductions in line edge roughness (LER: unevenness in lineend) and a line width roughness (LWR: unevenness in line width) on aline pattern are required.

This is because a width of a gate pattern, that is, a gate lengthgreatly influences transistor performance. Specifically, the LWR havinga period shorter than that of a transistor width Wg causes a shortchannel effect in which the gate length is locally shortened, so that aleakage current increases and a threshold voltage decreases. Meanwhile,the LWR having a period longer than that of the transistor width Wgcauses fluctuation of the gate length across a plurality of transistors,and causes a variation in transistor performance.

In this way, in recent years, along with the miniaturization of thesemiconductor device, a complication of a structure, and adiversification of materials, an improvement in an etching selectivitybetween the mask material and the material to be etched and a reductionin roughness are further required. As a technique of improving theetching selectivity, for example, PTL 1 discloses a method of improvinga selectivity between a mask material and a material to be etched byusing a gas capable of generating a deposition film containingcomponents same as those of the mask material.

CITATION LIST Patent Literature

-   PTL 1: JP-A-2013-118359

SUMMARY OF INVENTION Technical Problem

According to the technique in PTL 1, in a case where the mask materialis SiO and the material to be etched is SiN, or the mask material is TaNor WN and the material to be etched is Poly-Si, or the mask material isPoly-Si and the material to be etched is SiN as a combination of themask material and the material to be etched, it is possible to improvethe etching selectivity of the material to be etched with respect to themask material by generating the deposition film containing componentssame as those of the mask material on the mask material and selectingand using a gas in which the etching proceeds for one material to beetched.

As described above, in the case of a limited combination of the maskmaterial and the material to be etched, selective etching as describedabove can be performed by selecting a gas to be used. However, in recentyears, with the diversification of materials and the complication of thestructure, there is a case where it is very difficult to form thedeposition film containing components same as those of the maskmaterial, and to select a gas in which etching proceeds for one materialto be etched.

In the case of improving the etching selectivity, it is ideal that thedeposition film is formed on the mask material and the etching proceedsfor the material to be etched, but it is sufficient if the depositionfilm is formed on the mask material and no deposition film is formed onthe material to be etched. This is because that if the deposition filmis selectively formed only on the mask material, the mask heightincreases as a result, and it is possible to sufficiently secure aremaining amount of the mask height even if the selectivity of thematerial to be etched is low when etching the material to be etched inthe next step.

In the case of the EUV lithography technique, as described above, astructure in which the EUV resist is patterned on the SiARC or the SOGis generally used, and the SiARC or the SOG, which is the material to beetched, is etched using the EUV resist as the mask material. However,there is a problem that it is very difficult to form the deposition filmcontaining components same as those of the resist, which is the maskmaterial by the technique in PTL 1, to proceed the etching on the SiARCor the SOG, which is the material to be etched, or to select a gas inwhich the deposition film is not formed.

Meanwhile, in the case of the DSA lithography technique, there is only aslight difference in compositions among film structures of PS, PMMA, andthe NUL. In particular, for example, the NUL has a neutral filmstructure and has only a slight difference in composition, such as adiblock polymer containing about 50% PMMA and about 50% PS. In the caseof the DSA lithography technique, as described above, PMMA or the NUL,which is the material to be etched, is etched using PS as the maskmaterial. However, there is a problem that it is very difficult to formthe deposition film containing components same as those of PS, which isthe mask material by the technique in PTL 1, to proceed the etching onPMMA or the NUL, which is the material to be etched, or to select a gasin which the deposition film is not formed.

Therefore, when the material to be etched is etched using a patternformed by the EUV lithography technique and the DSA lithographytechnique as the mask material, a technique of improving the selectivityis required regardless of the gas. In addition, as an important problemin the EUV lithography technique and the DSA lithography technique, thereductions in LER roughness and in LWR roughness are increased, but PTL1 does not mention the reduction in roughness, and does not examine acountermeasure thereof. Therefore, along with the diversification ofmaterials and the complication of the structure, there has been a demandfor a technique of improving the selectivity and reducing the roughnessregardless of the gas.

The invention has been made in view of such a problem, and an objectthereof is to provide a plasma processing method capable of improvingthe etching selectivity of the material to be etched with respect to themask material and reducing the roughness of a side wall of the maskpattern.

Solution to Problem

In order to solve the above problem, a typical plasma processing methodaccording to the invention is

a plasma processing method of selectively depositing a deposition filmon a mask material with respect to a material to be etched, the plasmaprocessing method including

controlling an etching parameter so that an incubation time of the maskmaterial is shorter than an incubation time of the material to beetched.

Advantageous Effect

According to the invention, it is possible to provide a plasmaprocessing method capable of improving the etching selectivity of thematerial to be etched with respect to the mask material and reducing theroughness of the side wall of the mask pattern.

Problems, configurations, and effects other than those described abovewill be clarified by descriptions of the following embodiments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a configuration of a microwave plasmaetching apparatus applied to the invention.

FIG. 2 is a diagram showing an etching progress process in a case wherea resist formed by an EUV lithography is used as a mask material.

FIG. 3 is a diagram showing an EUV resist etching rate, a SiARC etchingrate, and a selectivity.

FIG. 4 is a diagram showing an EUV resist width and an LWR value.

FIG. 5 is a diagram showing an etching parameter adjustment procedureaccording to a first embodiment.

FIG. 6 is a diagram showing a microwave power supply power dependence ata first stage in a condition adjustment procedure according to a firstembodiment.

FIG. 7 is a diagram showing a radio frequency bias power supply powerdependence at a second stage in the condition adjustment procedureaccording to the first embodiment.

FIG. 8 is a diagram showing deposition rates of a deposition film on anEUV resist and of a deposition film on a SiARC at a third stage in thecondition adjustment procedure according to the first embodiment.

FIG. 9 is a diagram showing transitions in deposition amounts of thedeposition films on the EUV resist and on the SiARC, which can beestimated from results on FIG. 8 , and transitions in microwave powersupply power output and radio frequency bias power supply power outputat this time.

FIG. 10 is a diagram showing an incubation time in the first embodimentby extracting time 0 msec to 0.5 msec of the transition of thedeposition amount of the deposition film shown in FIG. 9 .

FIG. 11 is a diagram showing an etching progress process when using DSAlithography.

FIG. 12 a diagram showing a PS etching rate, a NUL etching rate, and aselectivity.

FIG. 13 is a diagram showing a PS width and a LWR value.

DESCRIPTION OF EMBODIMENTS

Hereinafter, each embodiment of the invention is described withreference to the drawings.

In the present embodiment, as a technique of improving a selectivity andreducing a roughness regardless of a gas, attention is paid to adifference in incubation times caused by a slight difference betweenstructures of a mask material and a material to be etched, and a filmthickness of a deposition film to be formed on each surface iscontrolled. The incubation time refers to a time from a start of filmformation to a time when a generated film formation species expands to asize of a critical nucleus and appears as a film. In addition, this timevaries even when there is only a slight difference in compositionbetween film structures of the mask material and the material to beetched. That is, the deposition film can be selectively deposited byutilizing the difference in incubation times.

In the present embodiment, a plasma processing method that selectivelydeposits the deposition film on the mask material with respect to thematerial to be etched includes controlling a plasma etching parameter(simply referred to as etching parameter) so that an incubation time ofthe mask material is shorter than an incubation time of the material tobe etched.

In addition, in the plasma processing method that selectively depositsthe deposition film on the mask material with respect to the material tobe etched, it is preferable to control the plasma etching parameter sothat the incubation time of the mask material is shorter than theincubation time of the material to be etched and the deposition film isnot deposited on the material to be etched.

Further, in the plasma processing method that selectively deposits thedeposition film on the mask material with respect to the material to beetched, it is preferable to control the plasma etching parameter so thatthe incubation time of the mask material is shorter than the incubationtime of the material to be etched and the etching proceeds withoutdepositing the deposition film on the material to be etched.

FIG. 1 shows a schematic cross sectional diagram of an electroncyclotron resonance (ECR) microwave plasma etching apparatus(hereinafter, also referred to as a “plasma processing apparatus”)according to an embodiment of the present invention. In the microwaveplasma etching apparatus, a shower plate 102 (for example, made ofquartz) for supplying an etching gas into a vacuum container 101 and adielectric window 103 (for example, made of quartz) are disposed in anupper portion of the vacuum container 101 whose upper portion is open,and the vacuum container 101 is sealed to form a processing chamber 104which is a plasma processing chamber. A gas supply device 105 forflowing the etching gas is connected to the shower plate 102.

Further, a vacuum exhaust device 106 is connected to the vacuumcontainer 101 via an exhaust on-off valve 117 and an exhaust ratevariable valve 118. The inside of the processing chamber 104 isdepressurized by opening the exhaust on-off valve 117 and driving thevacuum exhaust device 106, and is brought into a vacuum state in whichthe pressure is reduced from an atmospheric pressure. The pressure inthe processing chamber 104 is adjusted to a desired pressure by usingthe exhaust rate variable valve 118.

The etching gas is supplied from the gas supply device 105 into theprocessing chamber 104 via the shower plate 102, and is exhausted by thevacuum exhaust device 106 via the exhaust rate variable valve 118.

A sample mounting electrode 111, which is a sample stage, is provided ata lower portion of the vacuum container 101 so as to face the showerplate 102. In order to supply a first radio frequency power forgenerating plasma to the processing chamber 104, a waveguide 107 fortransmitting an electromagnetic wave is provided above the dielectricwindow 103. The electromagnetic wave to be transmitted to the waveguide107 is oscillated from an electromagnetic wave generating power supply109, which is a microwave power supply, via a matching unit 119. A pulsegenerating unit 121 is attached to the electromagnetic wave generatingpower supply 109, whereby microwaves can be pulse-modulated at any setrepetition frequency. A frequency of the electromagnetic wave is notparticularly limited, and in the present embodiment, a microwave of 2.45GHz is used.

A magnetic field generating coil 110 that generates a magnetic field isprovided outside the processing chamber 104, the electromagnetic waveoscillated from the electromagnetic wave generating power supply 109, byinteraction with the magnetic field generated by the magnetic fieldgenerating coil 110, generates high density plasma in the processingchamber 104, and an etching process is performed on a wafer 112 which isa sample and disposed on the sample mounting electrode 111 which is thesample stage.

The shower plate 102, the sample mounting electrode 111, the magneticfield generating coil 110, the exhaust on-off valve 117, the exhaustrate variable valve 118, and the wafer 112 are disposed coaxially withrespect to a central axis of the processing chamber 104, and therefore aflow of the etching gas, radicals and ions generated by the plasma, andreaction products generated by the etching are coaxially supplied to thewafer 112 and exhausted. This coaxial arrangement brings effects thatuniformity of an etching rate and an etching shape on a wafer plane isclose to axial symmetry, and the uniformity of a wafer processing isimproved.

The sample mounting electrode 111 is coated with a sprayed film (notshown) on an electrode surface thereof, and is connected to a DC powersupply 116 via a radio frequency filter 115. Further, a radio frequencybias power supply 114 is connected to the sample mounting electrode 111via a matching circuit 113. The radio frequency bias power supply 114 isconnected to the pulse generating unit 121 and can selectively supply atime-modulated second radio frequency power to the sample mountingelectrode 111. The frequency of the radio frequency bias is notparticularly limited, and in the present embodiment, a radio frequencybias of 400 kHz is used.

A control unit 120 that controls the above-mentioned ECR microwaveplasma etching apparatus, by an input unit (not shown), controls arepetition frequency or a duty ratio including an on/off timing ofpluses of the electromagnetic wave generating power supply 109, theradio frequency bias power supply 114, and the pulse generating unit121, and etching parameters such as a gas flow rate, a processingpressure, a microwave power, a radio frequency bias power, a coilcurrent, a pulse-on time, and a pulse-off-time for performing etching.

The duty ratio is a ratio of an on-period to one period of the pulse. Inthe present embodiment, the repetition frequency of the pulse can bechanged from 5 Hz to 10 kHz, and the duty ratio can be changed from 1%to 90%. Further, the setting of the time modulation may be an on-periodor an off-period. Next, each embodiment using the above-mentionedmicrowave plasma etching apparatus according to the present embodimentwill be described.

First Embodiment

FIG. 2 shows an etching progress process in a case where a resist formedby EUV lithography is used as the mask material. In the presentembodiment, a sample having a structure in which an EUV resist 203 ispatterned on a SiARC 202 formed on an organic planarization layer (OPL)201 is used. Alternatively, a sample having a structure in which the EUVresist is patterned on a SOG formed on a spin on carbon (SOC) may beused.

The etching in which the mask material is the EUV resist 203 and thematerial to be etched is the SiARC 202 proceeds in a direction of anarrow shown in FIG. 2 . FIG. 2 shows (a) a state before the etching, (b)a state during the etching, and a state (c) after the etching. At thistime, for example, when the EUV resist 203 and the SiARC 202 have thesame film thickness, a pattern width dimension is reduced if theselectivity during the etching is less than 1, and thus it is desirableto increase the selectivity during the etching, or to selectivelydeposit a deposition film on the EUV resist 203 to increase the filmthickness according to the mask material.

Here, the etching selectivity of the SiARC 202 with respect to the EUVresist 203 is a value obtained by dividing an etching rate of the SiARC202 by an etching rate of the EUV resist 203. When the film thickness ofthe EUV resist 203 is smaller than the film thickness of the SiARC 202,it is desirable to use a higher selectivity or to selectively deposit adeposition film with a larger film thickness on the EUV resist 203 tofurther increase the film thickness according to the mask material.

On the other hand, in order to reduce a roughness of a side wall of theEUV resist 203 before the etching from being transferred to a side wallof the SiARC 202 during the etching of the SiARC 202, it is desirable toreduce the roughness by selectively depositing a deposition film on theside wall of the EUV resist 203. Therefore, in order to improve theetching selectivity of the SiARC 202 with respect to the EUV resist 203as compared with related-art techniques and to reduce the roughness, itis necessary to selectively deposit a deposition film on an uppersurface and the side wall of the EUV resist 203.

At this time, when the deposition film is deposited on the upper surfaceof the SiARC 202, which is the material to be etched, the etching isinhibited, and therefore, the deposition film should not be deposited onthe upper surface of the SiARC 202, or the etching should be advanced.

The etching was performed using a mixed gas containing an Ar gas, a N₂gas, and a CH₄ gas under conditions of a gas pressure, a microwave powersupply power, a microwave power supply repetition frequency, a microwavepower supply duty ratio, a radio frequency bias power supply power, aradio frequency bias power supply repetition frequency, and a radiofrequency bias power supply duty ratio as shown in Table 1.

TABLE 1 AR gas 50 sccm N₂ gas 100 sccm CH₄ gas 2 sccm Gas pressure 15 PaMicrowave power supply power 800 W Microwave power supply 1 kHzrepetition frequency Microwave power supply duty 50% ratio Radiofrequency bias power 20 W supply power Radio frequency bias power 1 kHzsupply repetition frequency Radio frequency bias power 20% supply dutyratio

Under conditions of the present embodiment and conditions of ComparativeExample, samples before the etching shown in FIG. 2 were etched.Thereafter, the samples were cleaved, each cross section thereof wasobserved and the length was measured by a scanning electron microscope(SEM), and the etching rate, the etching selectivity, and the EUV resistwidth were compared and examined. In addition, an LWR roughness valuewas compared and examined with SEM observation and length measurementfrom directly above the sample.

FIG. 3 shows the etching rate and the etching selectivity. As shown inFIG. 3 , under the conditions of Comparative Example, the etchingselectivity of the SiARC with respect to the EUV resist is 2, which is avalue of 1 or more, and the etching rate of the EUV resist and theetching rate of the SiARC are positive, so that both the etching of theEUV resist and the etching of the SiARC are proceeding.

Meanwhile, under the conditions of the present embodiment, the etchingrate of the SiARC is lower than that under the conditions of ComparativeExample, and the etching rate of the EUV resist is a negative value,indicating that the deposition film is formed on the EUV resist.Therefore, under the conditions of the present embodiment, theselectivity of the SiARC with respect to the EUV resist is infinite.

Next, FIG. 4 shows the EUV resist width and the LWR value. Whenconditions before the etching are compared with the conditions ofComparative Example, the EUV resist width is slightly reduced and theLWR value is also slightly reduced due to the etching in the conditionsof Comparative Example. That is, it can be seen that the LWR value isslightly reduced as the etching proceeds in a horizontal direction ofthe EUV resist by the etching.

Meanwhile, under the conditions of the present embodiment, the EUVresist width is increased by about 2 nm, and the LWR value issignificantly reduced by about 30%. This indicates that, under theconditions of the present embodiment, the LWR value is alsosignificantly reduced by forming the deposition film on the side wall ofthe EUV resist. Thus, in the present embodiment, it is possible tosignificantly improve the etching selectivity of the SiARC with respectto the EUV resist and also significantly reduce the LWR value, ascompared with those under the conditions of Comparative Example.

Next, a condition adjustment procedure and a mechanism until theconditions of the present embodiment are reached will be described. Inthe present embodiment, the mixed gas containing the Ar gas, the N₂ gas,and the CH₄ gas as shown in Table 1 is used.

In the present embodiment, the Ar gas is used as a dilution gas.Alternatively, He, Ne, Kr, Xe, H₂, or the like, which is generally usedas the dilution gas, may be used. In addition, the CH₄ gas and the N₂gas are used as the gas for forming the deposition film. Alternatively,depending on the mask material and the material to be etched, which aretargets, and the condition adjustment procedure process to be describedlater, C₂H₂, C₂H₄, CHF₃, CH₃F, CH₂F₂, and the like, which are gasescontaining carbon C, may be used, and BN, NF₃, NCl₃, Nbr₃, and the like,which are gases containing nitrogen N, may be used.

The condition adjustment procedure is shown in FIG. 5 . At a first stageof the condition adjustment procedure, the microwave power supply poweris adjusted. At this time, as noted in FIG. 5 , the microwave powersupply power is not repeated, and a combination of the gases and the gaspressure may be set so that the deposition film is deposited on both themask material and the material to be etched. Therefore, the radiofrequency bias power supply power is set to 0 W in order to preventsputter etching due to ions.

Here, the film thickness of the deposition film is changed due to thegas flow rate, the gas pressure, and the microwave power supply power,and thus, for example, at the first stage of the condition adjustmentprocedure according to the first embodiment, a condition under which thefilm thickness of the deposition film is about 0 nm to 2 nm is adopted.

FIG. 6 shows the microwave power supply power dependence at the firststage of the condition adjustment procedure according to the firstembodiment. Here, the microwave power supply power is set to 800 W sothat the deposition rates of the deposition films on the EUV resist andon the SiARC are 0 nm/min to 2 nm/min.

Next, at a second stage of the condition adjustment procedure, the radiofrequency bias power supply power is adjusted. At this time, as shown inFIG. 5 , the radio frequency bias power supply power is not repeated,the microwave power supply is the same as that at the first stage, andthe second stage of the condition adjustment procedure according to thefirst embodiment adopts a condition that the deposition rate of thedeposition film is on the negative side, that is, is about 0 nm/min to−2 nm/min in which the etching proceeds.

FIG. 7 shows the radio frequency bias power supply power dependence atthe second stage of the condition adjustment procedure according to thefirst embodiment. Here, the radio frequency bias power supply power isset to 20 W so that the deposition rates of the deposition films on theEUV resist and on the SiARC are 0 nm/min to −2 nm/min.

An important matter up to the second stage of the condition adjustmentprocedure according the first embodiment is to determine conditionsunder which, taking a deposition rate of 0 nm/min for the depositionfilm as a center, a positive side by adjusting the microwave powersupply power, that is, a side where the deposition film is deposited, issymmetrical with a negative side by adjusting the radio frequency biaspower supply power, that is, a side where the etching is performed.Accordingly, with the microwave repetition frequency, the microwavepower supply duty ratio, the radio frequency bias power supplyrepetition frequency, and the radio frequency bias power supply dutyratio, which are adjusted at a third stage described below, thedeposition rates of the deposition films on the EUV resist and on theSiARC can be adjusted within a range of ±2 nm/min.

Next, at the third stage (adjustment stage) of the condition adjustmentprocedure according to the first embodiment, at a side where thedeposition rate of the deposition film on the EUV resist is positive,that is, a side where the deposition film is deposited, while at a sidewhere the deposition rate of the deposition film on the SiARC is 0nm/min or negative, that is, a side where the deposition film is notdeposited and the etching does not proceed, or a side where the etchingproceeds, the microwave power supply repetition frequency, the microwavepower supply duty ratio, the radio frequency bias power supplyrepetition frequency, and the radio frequency bias power supply dutyratio, which are the plasma etching parameters, are adjusted. That is,the etching parameter control includes a step of generating plasma bythe pulse-modulated first radio frequency power and a step of supplyingthe pulse-modulated second radio frequency power to the sample stage. Insuch a case, it is preferable that a period of a pulse that modulatesthe first radio frequency power is equal to a period of a pulse thatmodulates the second radio frequency power, and a duty ratio of thepulse that modulates the first radio frequency power is larger than aduty ratio of the pulse that modulates the second radio frequency power.

FIG. 8 shows the deposition rates of the deposition films on the EUVresist and on the SiARC at the third stage of the condition adjustmentprocedure according to the first embodiment. When the microwaverepetition frequency is set to 1 kHz, the microwave power supply dutyratio to 50%, the radio frequency bias power supply repetition frequencyto 1 kHz, and the radio frequency bias power supply duty ratio to 20%,the deposition rate of the deposition film on the EUV resist is 1.5nm/min and the deposition rate of the deposition film on the SiARC is−0.2 nm/min.

FIG. 9 shows transitions in deposition amounts of the deposition filmsof the EUV resist and the SiARC, which can be estimated from results ofFIG. 8 , and transitions in microwave power supply power and radiofrequency bias power supply power output at this time. Since therepetition frequencies of the microwave power supply power output andthe radio frequency bias power supply power are 1 kHz, one period isformed in 1 msec, and an output ON time is equal to the ratio of eachduty ratio.

When the microwave power supply power is OFF, plasma is not generated,and therefore the deposition of the deposition film or the etching doesnot proceed. Further, when the radio frequency bias power supply poweroutput is ON, the deposition rate is equal to or lower than the etchingrate, so that there is a side where the deposition film does not depositand the etching does not proceed, or the etching proceeds. Therefore,each transition in deposition amount of the deposition film on the EUVresist and on the SiARC follows a dotted line shown in FIG. 9 .

Here, in FIG. 10 , a time of 0 to 0.5 msec of the transition indeposition amount of the deposition film shown in FIG. 9 is extractedand the incubation time of the first embodiment will be described. Theincubation time of the deposition film deposited on the EUV resist is atime until the deposition is started, that is, a time until the graphhas a positive slope. Meanwhile, the incubation time of the depositionfilm deposited on the SiARC film is a time further repeated in additionto a period of 0.5 msec shown on the horizontal axis of the graph. Thatis, it can be said that the incubation time of the deposition film onthe EUV resist is shorter than the incubation time of the depositionfilm deposited on the SiARC.

Therefore, by adjusting the plasma etching parameters, that is, themicrowave power supply repetition frequency, the microwave power supplyduty ratio, the radio frequency bias power supply repetition frequency,and the radio frequency bias power supply duty ratio, it is possible tomake the incubation time of the deposition film deposited on the EUVresist as the mask material shorter than the incubation time of thedeposition film deposited on the SiARC as the material to be etched. Inorder to obtain a desired incubation time, it is sufficient to adjust atleast one value of the microwave power supply repetition frequency, themicrowave power supply duty ratio, the radio frequency bias power supplyrepetition frequency, and the radio frequency bias power supply dutyratio. This adjustment can be carried out by the control unit 120 in themicrowave plasma etching apparatus shown in FIG. 1 .

In the first embodiment, as shown in Table 1, the conditions of themicrowave power supply and the radio frequency bias power supply areoptimal. However, depending on the mask material and the material to beetched, which are targets, it is desired to appropriately select themicrowave power supply power, the radio frequency bias power supplypower, the microwave power supply repetition frequency, the radiofrequency bias power supply repetition frequency, the microwave powersupply duty ratio, and the radio frequency bias duty ratio and adjustaccording to the adjustment procedure in FIG. 5 to obtain optimalconditions.

Second Embodiment

FIG. 11 shows an etching progress process when using a DSA lithographytechnique. In the present embodiment, a sample having a structure inwhich PMMA 113 and PS 114 are patterned on a NUL 112 formed on SiN 111is used.

Firstly, a PS mask pattern is formed by etching PMMA, which is thematerial to be etched, using PS as the mask material. Next, the NUL isetched using the formed PS as the mask pattern. The etching proceeds ina direction of an arrow shown in FIG. 11 . FIG. 11 shows (a) a statebefore the etching, (b) a state after the PMMA etching, and (c) a stateafter the NUL etching.

In the present embodiment, a case where it is applied to the NUL etchingwill be described. The etching was performed using a mixed gascontaining an Ar gas, a N₂ gas, and a CH₄ gas and conditions of a gaspressure, a microwave power supply power, a microwave power supplyrepetition frequency, a microwave power supply duty ratio, a radiofrequency bias power supply power, a radio frequency bias power supplyrepetition frequency, and a radio frequency bias power supply duty ratioas shown in Table 2. Under conditions of the present embodiment andconditions of Comparative Example, samples after the PMMA etching shownin FIG. 11 were etched.

TABLE 2 AR gas 300 sccm N₂ gas 30 sccm CH₄ gas 10 sccm Gas pressure 3.5Pa Microwave power supply power 800 W Microwave power supply repetition1 kHz frequency Microwave power supply duty ratio 50% Radio frequencybias power supply 50 W power Radio frequency bias power supply 1 kHzrepetition frequency Radio frequency bias power supply 50% duty ratio

Thereafter, the samples were cleaved, each cross section thereof wasobserved and the length was measured by a scanning electron microscope(SEM), and the etching rate, the etching selectivity, and the PS widthwere compared and examined. In addition, the LWR roughness value wascompared and examined with SEM observation and length measurement fromdirectly above the sample.

FIG. 12 shows the etching rate and the etching selectivity. As shown inFIG. 12 , under the conditions of Comparative Example, the etchingselectivity of the NUL with respect to PS is 1.5, which is a value of 1or more, and the etching rate of PS and the etching rate of the NUL arepositive, so that both the etching of PS and the etching of the NUL areproceeding.

Meanwhile, under the conditions of the present embodiment, the etchingrate of the NUL is lower than that under the conditions of ComparativeExample, but the etching rate of PS is a negative value, indicating thatthe deposition film is formed on PS. Therefore, under the conditions ofthe present embodiment, the selectivity of the NUL with respect to PS isinfinite.

Next, FIG. 13 shows the PS width and the LWR value. When conditionsafter the PMMA etching and the conditions of Comparative Example arecompared, the PS width is slightly reduced and the LWR value is alsoslightly reduced due to the etching in the conditions of ComparativeExample. That is, it can be seen that the LWR value is slightly reducedas the etching proceeds in the horizontal direction of the EUV resist bythe etching.

Meanwhile, under the conditions of the present embodiment, the PS widthis increased by about 2 nm, and the LWR value is significantly reducedby about 60%. This indicates that, under the conditions of the presentembodiment, the LWR value is also significantly reduced by forming thedeposition film on the side wall of PS. Thus, in the present embodiment,it is possible to significantly improve the etching selectivity of theNUL with respect to PS and also significantly reduce the LWR value, ascompared with those under the conditions of Comparative Example. Thecondition adjustment procedure up to the conditions of the presentembodiment is carried out according to FIG. 5 .

In the present embodiment, an application example in an electroncyclotron resonance (ECR) type microwave plasma etching apparatus usingmicrowaves has been described, but the present invention is not limitedthereto. The plasma processing method may be applied to a plasma etchingapparatus using a capacitive coupling type or inductive coupling typeplasma generating unit. In addition, it is preferable that the etchingparameter is controlled using a mixed gas containing an argon gas, anitrogen gas, and a methane gas.

Further, in the present embodiment, after the deposition film is formedin the processing chamber of the etching apparatus, an etchingprocessing is continuously performed in the same processing chamber. Asa method of forming the deposition film generally used in amanufacturing process of a semiconductor device, there is a film formingapparatus using an evaporation method, a sputtering method, a vaporphase growth method, an atomic layer deposition (ALD) method, or thelike. When the deposition film is formed according to the presentembodiment by using these film forming apparatuses, a time for conveyingthe wafer from the processing chamber of the film forming apparatus tothe processing chamber of the etching apparatus or from the processingchamber of the etching apparatus to the processing chamber of the filmforming apparatus is required, and the throughput is decreased. Inaddition, when the processing chamber of the film forming apparatus andthe processing chamber of the etching apparatus are not connected via avacuum conveyance path, the wafer is exposed to the atmosphere duringconveying, and therefore the pattern surface after film formation oretching reacts with components in the atmosphere (nitrogen, oxygen,etc.) to deteriorate the film quality, which hinders the subsequentprocessing. Further, when the deposition film is formed on the side wallof a fine mask pattern by the EUV and DSA lithography techniques used inthe present embodiment, an ALD apparatus using an ALD method isconsidered to be suitable, but due to the principle of the ALD method,the deposition film is formed on the side wall of the pattern and at thesame time, the deposition film is also formed on the bottom surface ofthe pattern, which hinders the subsequent etching processing. Therefore,it can be said that the method of forming the deposition film andperforming the etching processing in the processing chamber of theetching apparatus shown in the present embodiment is optimal.

As described above, the plasma etching method of the present embodimentselectively deposits the deposition film on the mask material withrespect to the material to be etched, and therefore the plasma etchingparameter is controlled so that the incubation time of the depositionfilm deposited on the mask material is shorter than the incubation timeof the deposition film deposited on the material to be etched.Therefore, it is possible to significantly improve the etchingselectivity of the material to be etched with respect to the maskmaterial and significantly reduce the roughness of the side wall of themask pattern as compared with the technique of Comparative Example.

REFERENCE SIGN LIST

-   -   101 vacuum container    -   102 shower plate    -   103 dielectric window    -   104 processing chamber    -   105 gas supply device    -   106 vacuum exhaust device    -   107 waveguide    -   109 electromagnetic wave generating power supply    -   110 magnetic field generating coil    -   111 sample mounting electrode    -   112 wafer    -   113 matching circuit    -   114 radio frequency bias power supply    -   115 radio frequency filter    -   116 DC power supply    -   117 exhaust on-off valve    -   118 exhaust rate variable valve    -   119 matching unit    -   120 control unit    -   121 pulse generating unit

1. A plasma processing method of selectively depositing a depositionfilm on a mask material with respect to a material to be etched, theplasma processing method comprising: controlling an etching parameter sothat an incubation time of the mask material is shorter than anincubation time of the material to be etched.
 2. The plasma processingmethod according to claim 1, wherein the etching parameter controlincludes a step of generating a plasma by a pulse-modulated first radiofrequency power, and a step of supplying a pulse-modulated second radiofrequency power to a sample stage on which a sample on which thematerial to be etched is deposited is placed.
 3. The plasma processingmethod according to claim 1, wherein the mask material is an EUV resistand the material to be etched is a SiARC.
 4. The plasma processingmethod according to claim 1, wherein the mask material is PS and thematerial to be etched is PMMA.
 5. The plasma processing method accordingto claim 1, wherein the etching parameter control is performed using amixed gas of an argon gas, a nitrogen gas, and a methane gas.
 6. Theplasma processing method according to claim 2, wherein the etchingparameter control is performed using a mixed gas of an argon gas, anitrogen gas, and a methane gas.
 7. The plasma processing methodaccording to claim 2, wherein a period of a pulse that modulates thefirst radio frequency power and a period of a pulse that modulates thesecond radio frequency power are equal to each other, and a duty ratioof the pulse that modulates the first radio frequency power is largerthan a duty ratio of the pulse that modulates the second radio frequencypower.
 8. The plasma processing method according to claim 7, wherein themask material is an EUV resist and the material to be etched is a SiARC.